Light sources are nowadays applied in lighting systems consisting of a large number of light sources. Since the introduction of solid state lighting several parameters of these light sources can be varied and controlled in a system of light sources. Such parameters include light intensity, light color, light color temperature and even light direction. By varying and controlling these parameters of the different light sources, a light designer or user of the system is enabled to generate lighting scenes. This process is often referred to as scene setting, and is typically quite a complex process due to the multitude of light sources and parameters to be controlled. Typically one controller, or control channel, is required for each light source. This makes it difficult to control a system of more than ten light sources.
To enable a more intuitive and simpler control of the light sources, and to create scenes, the embedding of invisible identifiers in the light output of luminaires has been previously proposed. This embedding of identifiers can be based on unique modulation of the visible light (VL) of the luminaire or by placing of an additional infra-red (IR) light source in the luminaire and uniquely modulate this IR light. The embedding of identifiers in the light will be referred to as coded light (CL).
For the transmission of CL, mostly, light emitting diodes (LEDs) are considered, which allow for a reasonable high modulation frequency and bandwidth. This in turn may result in a fast response of the control system. The identifiers can, however, also be embedded in the light of other light sources, such as incandescent, halogen, fluorescent (FL) and high-intensity discharge (HID) lamps.
These light source identifiers, also referred to as codes, allow for the identification and strength estimation of the individual local illumination contributions. This can be applied in light control applications such as commissioning, light source selection and interactive scene setting. These applications have use in, for example, homes, offices, shops and hospitals. These light source identifiers hence enable a simple and intuitive control operation of a light system, which might otherwise be very complex.
Illumination systems based on LEDs normally consist of a large number, e.g. hundreds, of spatially distributed LEDs. This is partly because a single state-of-the-art LED still cannot provide sufficient illumination and since LEDs are point sources. Due to the large number of LEDs and the broad range of illumination levels that can be supported by each LED, the complexity to calibrate and control such a lighting system is quite high. According to state-of-the-art techniques only a limited number (e.g. up to 100) light sources can be identified in a coded light system.